Tracking traumatic head injuries with the chemical senses.

Chemosensory disorders, primarily olfactory, have diagnostic significance for prevalent human illnesses, but the multitude of smells makes measuring function appear daunting. The olfactory system operates under dynamic natural sensing conditions in which many individual odor chemicals are waxing and waning. Yet, in experimentally controlled simulations, mixture-component selective adaptation shows individual or shared prominent characteristic odors are detected but molecular stimulus features are not.

Recognition of the Component Odors in Mixtures.

Natural olfactory stimuli are volatile-chemical mixtures in which relative perceptual saliencies determine which odor-components are identified. Odor identification also depends on rapid selective adaptation, as shown for 4 odor stimuli in an earlier experimental simulation of natural conditions. Adapt-test pairs of mixtures of water-soluble, distinct odor stimuli with chemical features in common were studied.

Taste bud leptin: sweet dampened at initiation site.

The intriguing observation that leptin decreases sweet-evoked peripheral gustatory responses has aroused much interest (Kawai K, Sugimoto K, Nakashima K, Miura H, Ninomiya Y. 2000. Leptin as a modulator of sweet taste sensitivities in mice.

Gustatory, trigeminal, and olfactory aspects of nicotine intake in three mouse strains.

Studies of nicotine consumption in rodents often intend to investigate nicotine's post-absorptive effects, yet little is known about the pre-absorptive sensory experience of nicotine drinking, including gustatory, trigeminal, and olfactory influences. We conditioned taste aversion (CTA) to nicotine in males of 3 inbred mouse strains: C57BL/6J, DBA/2J, and 129X1/SvJ by repeatedly pairing 150 μg/ml nicotine drinking with lithium chloride injections. Generalization to a variety of bitter, sour, sweet, salty, and irritant solutions and to nicotine odor was then examined.

Effects of selective adaptation on coding sugar and salt tastes in mixtures.

Little is known about coding of taste mixtures in complex dynamic stimulus environments. A protocol developed for odor stimuli was used to test whether rapid selective adaptation extracted sugar and salt component tastes from mixtures as it did component odors. Seventeen human subjects identified taste components of "salt + sugar" mixtures.

Amiloride-sensitive and amiloride-insensitive responses to NaCl + acid mixtures in hamster chorda tympani nerve.

Component signaling in taste mixtures containing both beneficial and dangerous chemicals depends on peripheral processing. Unidirectional mixture suppression of chorda tympani (CT) nerve responses to sucrose by quinine and acid is documented for golden hamsters (Mesocricetus auratus). To investigate mixtures of NaCl and acids, we recorded multifiber responses to 50 mM NaCl, 1 and 3 mM citric acid and acetic acid, 250 μM citric acid, 20 mM acetic acid, and all binary combinations of each acid with NaCl (with and without 30 μM amiloride added).

B6-MSM consomic mouse strains reveal multiple loci for genetic variation in sucrose octaacetate aversion.

Based on crosses among inbred strains derived principally from M. m. domesticus, sucrose octaacetate (SOA) aversion in laboratory mice has been thought for many years to be controlled by a single genetic locus (Soa) located on distal chromosome (Chr) 6.

Time and intensity factors in identification of components of odor mixtures.

Identification of odors of compounds introduced into changeable olfactory environments is the essence of olfactory coding, which focuses perception on the latest stimulus with the greatest salience. Effects of stimulus intensity and adapting time on mixture component identification after adapting with one component were each studied in 10 human subjects. Odors of 1 and 5 mM vanillin (vanilla) and phenethyl alcohol (rose) were identified, with adapting time varied by sniffing naturally once or twice, or sniffing 5 times, once every 2 s.

Taste coding after selective inhibition by chlorhexidine.

Coding of the complex tastes of ionic stimuli in humans was studied by combining taste confusion matrix (TCM) methodology and treatment with chlorhexidine gluconate. The TCM evaluates discrimination of multiple stimuli simultaneously. Chlorhexidine, a bis-biguanide antiseptic, reversibly inhibits salty taste and tastes of a subset of bitter stimuli, including quinine hydrochloride.

Responses of the hamster chorda tympani nerve to sucrose+acid and sucrose+citrate taste mixtures.

Studies of taste receptor cells, chorda tympani (CT) neurons, and brainstem neurons show stimulus interactions in the form of inhibition or enhancement of the effectiveness of sucrose when mixed with acids or citrate salts, respectively. To investigate further the effects of acids and the trivalent citrate anion on sucrose responses in hamsters (Mesocricetus auratus), we recorded multifiber CT responses to 100 mM sucrose; a concentration series of HCl, citric acid, acetic acid, sodium citrate (with and without amiloride added), potassium citrate, and all binary combinations of acids and salts with 100 mM sucrose. Compared with response additivity, sucrose responses were increasingly suppressed in acid + sucrose mixtures with increases in titratable acidity, but HCl and citric acid were more effective suppressors than acetic acid.

Salt taste inhibition by cathodal current.

Effects of cathodal current, which draws cations away from the tongue and drives anions toward the tongue, depend on the ionic content of electrolytes through which the current is passed. To address the role of cations and anions in human salt tastes, cathodal currents of -40 microA to -80 microA were applied to human subjects' tongues through supra-threshold salt solutions. The salts were sodium chloride, sodium bromide, potassium chloride, ammonium chloride, calcium chloride, sodium nitrate, sodium sulfate, sodium saccharin, sodium acetate and sodium benzoate, which taken together encompass salty, bitter, sour and sweet taste qualities.

Cracking taste codes by tapping into sensory neuron impulse traffic.

Insights into the biological basis for mammalian taste quality coding began with electrophysiological recordings from "taste" nerves and this technique continues to produce essential information today. Chorda tympani (geniculate ganglion) neurons, which are particularly involved in taste quality discrimination, are specialists or generalists. Specialists respond to stimuli characterized by a single taste quality as defined by behavioral cross-generalization in conditioned taste tests.

Regional specificity of chlorhexidine effects on taste perception.

Chlorhexidine (CHX) gluconate, a bitter bis-biguanide antiseptic, reduces the intensity of the salty taste of NaCl and bitter taste of quinine in humans. This study addresses regional specificity of CHX's effects on taste. Perceptual intensity and quality were measured for separate taste bud containing oral loci innervated either by afferent fibers of cranial nerve (CN) VII or CN IX.

Cycloheximide: no ordinary bitter stimulus.

Cycloheximide (CyX), a toxic antibiotic with a unique chemical structure generated by the actinomycete, Streptomyces griseus, has emerged as a primary focus of studies on mammalian bitter taste. Rats and mice avoid it at concentrations well below the thresholds for most bitter stimuli and T2R G-protein-coupled receptors specific for CyX with appropriate sensitivity are identified for those species. Like mouse and rat, golden hamsters, Mesocricetus auratus, also detected and rejected micromolar levels of CyX, although 1mM CyX failed to activate the hamster chorda tympani nerve.

Characteristic component odors emerge from mixtures after selective adaptation.

Humans cannot reliably identify the distinctive characteristic odors of components in mixtures containing more than three compounds. In the present study, we demonstrate that selective adaptation can improve component identification. Characteristic component odors, lost in mixtures, were identifiable after presenting other mixture constituents for a few seconds.

Peripheral gustatory processing of sweet stimuli by golden hamsters.

Behaviors and taste-nerve responses to bitter stimuli are linked to compounds that bind T2 receptors expressed in one subset of taste-bud receptor cells (TRCs); and behavioral and neural responses to sweet stimuli are linked to chemical compounds that bind a T1 receptor expressed in a different TRC subset. Neural and behavioral responses to bitter-sweet mixtures, however, complicate the ostensible bitter and sweet labeled lines. In the golden hamster, Mesocricetus auratus, quinine hydrochloride, the bitter prototype, suppresses chorda tympani (CT) nerve responses to the sweet prototype: sucrose.

Variation in intake of sweet and bitter solutions by inbred strains of golden hamsters.

Variation in intake of sweet and bitter solutions by inbred strains of laboratory mice has helped identify genes related to taste behaviors; but similar information is not available for golden hamsters (Mesocricetus auratus ), a species used much in taste research. Thus, 6-hour, 1-bottle intake by water-replete hamsters of 7 inbred strains was measured for water and 2 concentrations of sucrose, maltose, D-phenylalanine (D-Phe), and sodium saccharin, which are sweet; and quinine.HCl, L-phenylalanine (L-Phe), caffeine, and sucrose octaacetate (SOA), which are bitter to humans.

The distinctiveness of ionic and nonionic bitter stimuli.

The diverse chemical structures of stimuli that are bitter to humans suggest a need for multiple bitter receptors. Reactions of golden hamsters (Mesocricetus auratus) to 1 mM quinine hydrochloride, 3 mM denatonium benzoate, 180 mM magnesium sulfate, 30-100 mM caffeine, and 1-1.5 mM sucrose octaacetate (SOA) were studied to address whether there are multiple sensations elicited by bitter stimuli.

The effect of orthognathic surgery on taste function on the palate and tongue.

Purpose: Perceived taste intensity and taste quality identification on localized regions of the palate and tongue were examined for 9 patients before orthognathic surgery and again at 1 to 2 and 6 to 9 months after surgery. Taste function would be at risk on the palate after maxillary Le Fort I osteotomy (LFI) and on the tongue after mandibular sagittal split osteotomy (SSO) because of potential damage to peripheral nerves conducting afferent chemosensory information from these regions.

Patients And Methods: Three patients had LFI and SSO, 1 had LFI only, and 5 had SSO only.

Taste responses to mixtures: analytic processing of quality.

The tastes of 100 mM sodium chloride (NaCl), 100 mM sucrose, and 1 mM quinine hydrochloride in mixtures were investigated in golden hamsters (Mesocricetus auratus) with a conditioned taste aversion (CTA) paradigm. CTAs, established in golden hamsters by injection of lithium chloride, were quantified as percent suppression of control 1-hr stimulus intake. CTAs for 10 of 15 stimulus pairs with common components symmetrically cross-generalized, suggesting that component qualities were recognized in binary and ternary mixtures.

Taste confusions following chlorhexidine treatment.

Chlorhexidine, a bitter bis-biguanide antiseptic, is the only known blocker of the human salty taste. In order to characterize the effects of chlorhexidine on stimulus identification, taste confusion matrix (TCM) performance was measured for subjects treated with 1.34 mM chlorhexidine gluconate (n = 9) and water controls (n = 9).